In the title adduct, C6H5NO3·0.5C4H10N2, the piperazine ring possesses inversion symmetry and has a chair conformation. Its mean plane makes a dihedral angle of 65.45 (7)° with the 4-nitrophenol ring. In the crystal, the piperazine ring is linked to two 4-nitrophenol molecules via O-HN hydrogen bonds. The molecules are also linked via bifurcated N-H(O,O) hydrogen bonds involving the NO2 O atoms, forming a two-dimensional network lying parallel to (102). The networks are linked via C-HO hydrogen bonds, forming a three-dimensional structure.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2605 ).

Acknowledgements

The authors thank the TBI X-ray facility, CAS in Crystallography and Biophysics, University of Madras, India, for the data collection. TS and DV thank the UGC (SAP-CAS) for the departmental facilities. TS also thanks DST Inspire for a fellowship.

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